The present invention relates to a semiconductor assembling method and apparatus for joining semiconductor chips with lead frames and the like in semiconductor fabrication processes.
Semiconductor chips are connected with external electrodes, such as lead frames, by means of a wire made of gold, aluminium or the like and by using a wire bonder. This wire is connected with the semiconductor chips or external electrodes by heat or ultrasonic waves or by both.
Among the wire bonders, in each of those using the bonding process so called ball bonding, a ball is formed at the tip of the wire by electric discharge or other heating means. The junction conditions for this process include the temperature of the stage at which semiconductor chips and external electrodes are heated, the pressure with which the wire is pressed as well as its time, and the oscillation output of ultrasonic waves as well as its time.
These conditions are previously stored as data in the wire bonder. These data are given as fixed data in all, or fixed data for each wire.
In the case where the wire bonder performs bonding processes continuously for a plurality of wires, the pressurizing tool receives heat from the semiconductor chip heater, resulting in a temperature rise. The ball also comes to a high temperature because the bonding process is carried out immediately after the formation of the ball.
However, when the interval from one bonding process to another is prolonged, for example, during the transfer of semiconductor chips or at a restart after a halt, the temperature of the pressurizing tool or the ball would lower. This poses an issue that the alloying of the wire and the semiconductor chip is suppressed such that a deterioration in the bondability may occur.